Relay Voltage Control for Inrush Prevention
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Solution Overview
Problem
Conventional inrush current prevention circuits fail to safely switch between contact and holding voltages in relays, leading to potential contact failures when power supply abnormalities occur, especially in compact relays requiring voltage transitions.
Innovation Solution
A power conversion device with a DC converting circuit, an inrush prevention circuit, and a controller that determines whether to apply a contact voltage or a holding voltage based on power supply and smoothing capacitor voltage information, ensuring safe operation by controlling the relay voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a relay is designed with reduced size and increased capacity, then the relay becomes more compact and inexpensive, but the relay requires voltage transition from contact voltage to holding voltage which may cause contact failure during power supply abnormalities
Solution Approach 1:
The control device monitors the power supply voltage before abnormality occurs and prepares the relay control strategy in advance. When power supply abnormality is detected, the control device has already determined whether to apply contact voltage or holding voltage based on pre-monitored voltage information, enabling immediate appropriate response without delay
Solution Approach 2:
The control device continuously monitors power supply voltage information and smoothing capacitor voltage information, using this feedback to dynamically determine the appropriate voltage level (contact or holding) to apply to the relay. This closed-loop control ensures the relay receives the correct voltage under varying power supply conditions
2Device complexity
If the contact voltage and holding voltage are set at the same level, then the relay control is simpler and no monitoring is needed, but this approach cannot be applied to compact relays that require voltage transition
Solution Approach 1:
The control device dynamically adjusts the relay voltage level based on real-time monitoring of power supply voltage and smoothing capacitor voltage. The system transitions from a static fixed-voltage approach to a dynamic adaptive approach, changing the voltage level (contact or holding) according to the actual power supply condition and capacitor charge state
Solution Approach 2:
The control device changes the voltage parameter applied to the relay based on monitored conditions. By comparing power supply voltage information and smoothing capacitor voltage information, the control device selects between contact voltage and holding voltage, effectively changing the electrical parameter to match operational requirements
Data Source
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AI summary
The purpose of the present invention is to safely use a relay without causing a contact failure in an inrush prevention circuit of a power conversion device, said relay switching between a voltage at contact time and a voltage at hold time. The power conversion device is provided with: a DC conversion unit for converting an AC voltage to a DC voltage; an inrush prevention circuit equipped with a resistor one end of which is connected to the DC conversion unit, and a relay connected to the resistor in parallel; a DC smoothing unit equipped with a smoothing capacitor connected to the other end of the resistor; and a control unit for controlling the inrush prevention circuit. The control unit determines, on the basis of voltage information of a power supply for operating the relay and voltage information of the smoothing capacitor, whether to apply a contact voltage to the relay or to apply a hold voltage smaller than the contact voltage to the relay.